| 1. |
- Aben, Ralf C. H., et al.
(författare)
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Cross continental increase in methane ebullition under climate change
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4) strongly contributes to observed global warming. As natural CH4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. Here we show a remarkably strong relationship between CH4 ebullition and temperature across a wide range of freshwater ecosystems on different continents using multi-seasonal CH4 ebullition data from the literature. As these temperature-ebullition relationships may have been affected by seasonal variation in organic matter availability, we also conducted a controlled year-round mesocosm experiment. Here 4 degrees C warming led to 51% higher total annual CH4 ebullition, while diffusion was not affected. Our combined findings suggest that global warming will strongly enhance freshwater CH4 emissions through a disproportional increase in ebullition (6-20% per 1 degrees C increase), contributing to global warming.
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| 2. |
- Bansal, Sheel, et al.
(författare)
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Practical Guide to Measuring Wetland Carbon Pools and Fluxes
- 2023
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Ingår i: Wetlands (Wilmington, N.C.). - : SPRINGER. - 0277-5212 .- 1943-6246. ; 43:8
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Forskningsöversikt (refereegranskat)abstract
- Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions.
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| 3. |
- Linkhorst, Annika, et al.
(författare)
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Comparing methane ebullition variability across space and time in a Brazilian reservoir
- 2020
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 65:7, s. 1623-1634
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Tidskriftsartikel (refereegranskat)abstract
- The potent greenhouse gas methane (CH4) is readily emitted from tropical reservoirs, often via ebullition (bubbles). This highly stochastic emission pathway varies in space and time, however, hampering efforts to accurately assess total CH4 emissions from water bodies. We systematically studied both the spatial and temporal scales of ebullition variability in a river inflow bay of a tropical Brazilian reservoir. We conducted multiple highly resolved spatial surveys of CH4 ebullition using a hydroacoustic approach supplemented with bubble traps over a 12‐month and a 2‐week timescale to evaluate which scale of variation was more important. To quantify the spatial and temporal variability of CH4 ebullition, we used the quartile coefficients of dispersion at each point in space and time and compared their frequency distributions across the various temporal and spatial scales. We found that CH4 ebullition varied more temporally than spatially and that the intra‐annual variability was stronger than daily variability within 2 weeks. We also found that CH4 ebullition was positively related to water temperature increase and pressure decrease, but no consistent relationship with water column depth or sediment characteristics was found, further highlighting that temporal drivers of emissions were stronger than spatial drivers. Annual estimates of CH4 ebullition from our study area may vary by 75–174% if ebullition is not resolved in time and space, but at a minimum we recommend conducting spatially resolved measurements at least once during each major hydrologic season in tropical regions (i.e., in dry and rainy season when water levels are falling and rising, respectively).
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| 4. |
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| 5. |
- Linkhorst, Annika, et al.
(författare)
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Spatially Resolved Measurements in Tropical Reservoirs Reveal Elevated Methane Ebullition at River Inflows and at High Productivity
- 2021
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 35:5
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of rivers are being dammed, particularly in the tropics, and reservoir water surfaces can be a substantial anthropogenic source of greenhouse gases. On average, 80% of the CO2-equivalent emission of reservoirs globally has been attributed to CH4, which is predominantly emitted via ebullition. Since ebullition is highly variable across space and time, both measuring and upscaling to an entire reservoir is challenging, and estimates of reservoir CH4 emission are therefore not well constrained. We measured CH4 ebullition at high spatial resolution with an echosounder and bubble traps in two reservoirs of different use (water storage and hydropower), size and productivity in the tropical Brazilian Atlantic Rainforest biome. Based on the spatially most well-resolved whole-reservoir ebullition measurements in the tropics so far, we found that mean CH4 ebullition was twice as high in river inflow areas than in other parts of the reservoirs, and more than four times higher in the eutrophic reservoir compared to the oligotrophic one. Using different upscaling approaches rendered similar whole-reservoir CH4 ebullition estimates, suggesting that highly spatially resolved measurements may be more important for constraining reservoir-wide CH4 estimates than choice of upscaling approach. The minimum sampling effort was high (>250 and >1700 30-m segments of hydroacoustic survey to reach within 50% or 80% accuracy, respectively). This suggests that traditional manual bubble trap measurements should be abandoned in favour of highly resolved measurements in order to get spatially representative estimates of CH4 ebullition, which accounted for 60 and 99% of total C emission in the two studied reservoirs.
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| 6. |
- Prairie, Yves T., et al.
(författare)
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Greenhouse Gas Emissions from Freshwater Reservoirs : What Does the Atmosphere See?
- 2018
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 21:5, s. 1058-1071
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater reservoirs are a known source of greenhouse gas (GHG) to the atmosphere, but their quantitative significance is still only loosely constrained. Although part of this uncertainty can be attributed to the difficulties in measuring highly variable fluxes, it is also the result of a lack of a clear accounting methodology, particularly about what constitutes new emissions and potential new sinks. In this paper, we review the main processes involved in the generation of GHG in reservoir systems and propose a simple approach to quantify the reservoir GHG footprint in terms of the net changes in GHG fluxes to the atmosphere induced by damming, that is, ´€˜what the atmosphere sees’. The approach takes into account the pre-impoundment GHG balance of the landscape, the temporal evolution of reservoir GHG emission profile as well as the natural emissions that are displaced to or away from the reservoir site resulting from hydrological and other changes. It also clarifies the portion of the reservoir carbon burial that can potentially be considered an offset to GHG emissions.
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| 7. |
- Sobek, Sebastian, et al.
(författare)
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Extreme organic carbon burial fuels intense methane bubbling in a temperate reservoir
- 2012
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 39:1, s. L01401-
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Tidskriftsartikel (refereegranskat)abstract
- Organic carbon (OC) burial and greenhouse gas emission of inland waters plays an increasingly evident role in the carbon balance of the continents, and particularly young reservoirs in the tropics emit methane (CH(4)) at high rates. Here we show that an old, temperate reservoir acts simultaneously as a strong OC sink and CH(4) source, because the high sedimentation rate supplies reactive organic matter to deep, anoxic sediment strata, fuelling methanogenesis and gas bubble emission (ebullition) of CH(4) from the sediment. Damming of the river has resulted in the build-up of highly methanogenic sediments under a shallow water column, facilitating the transformation of fixed CO(2) to atmospheric CH(4). Similar high OC burial and CH(4) ebullition is expected in other reservoirs and natural river deltas.
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